Ultragenyx ends three GTX-102 trials in Angelman syndrome for lack of efficacy

Ultragenyx Pharmaceutical Inc has terminated three clinical trials of GTX-102, also known as apazunersen, an antisense oligonucleotide being studied in Angelman syndrome. Clinicaltrials.gov records for all three studies list the same reason for stopping: lack of efficacy¹, with each record's last update posted on 2026-11-03.

The Phase 3 "Aspire" trial (NCT06617429, GTX-102-CL301) was designed as a randomized, double-blind, sham-controlled study investigating the efficacy and safety of GTX-102 in pediatric subjects with Angelman syndrome², with a primary goal of measuring the effect of GTX-102 in cognitive function in participants with deletion-type Angelman Syndrome². The study enrolled 129 participants² and was terminated for lack of efficacy², with a start date of 2024-12-03, primary completion on 2026-07-10, and study completion on 2026-10-30.

The Phase 2 basket study "Aurora" (NCT07157254, GTX-102-CL210) tested GTX-102 across genotypes and age groups¹ of Angelman syndrome through four subprotocols. That trial enrolled 55 participants¹ and had a start date of 2025-10-13, with both primary completion and study completion listed as 2026-10-30, before being terminated for lack of efficacy.

The long-term extension study (NCT06415344, GTX-102-CL302), intended to evaluate the long-term safety profile of GTX-102 in participants with Angelman Syndrome³, had enrolled 66 participants³ and was open to those rolling over from a prior GTX-102 clinical study³. It began on 2024-07-31 and was also terminated for lack of efficacy, with both completion dates listed as 2026-10-30.